Process for removal of photoresist mask used for making vias in low k carbon-doped silicon oxide dielectric material, and for removal of etch residues from formation of vias and removal of photoresist mask

ABSTRACT

A process for removal of a photoresist mask used to etch openings in low k carbon-doped silicon oxide dielectric material of an integrated circuit structure, and for removing etch residues remaining from either the etching of the openings or removal of the resist mask, while inhibiting damage to the low k dielectric material comprises. The structure is exposed to a reducing plasma to remove a portion of the photoresist mask, and to remove a portion of the residues remaining from formation of the openings in the layer of low k dielectric material. The structure is then exposed to an oxidizing plasma to remove any remaining etch residues from the openings in the layer of low k dielectric material or removal of the resist mask.

CROSS-REFERENCE TO RELATED APPLICATIONS

The subject matter of this application relates to the subject matter ofHu U.S. Pat. No. 6,316,354, issued Nov. 13, 2001 entitled “PROCESS FORREMOVING RESIST MASK OF INTEGRATED CIRCUIT STRUCTURE WHICH MITIGATESDAMAGE TO UNDERLYING LOW DIELECTRIC CONSTANT SILICON OXIDE DIELECTRICLAYER”, assigned to the assignee of this application, and the subjectmatter of which is hereby incorporated by reference.

The subject matter of this application also relates to the subjectmatter of Gu et al. U.S. Pat. No. 6,562,700, issued May 13, 2003,entitled “PROCESS FOR REMOVAL OF RESIST MASK OVER LOW K CARBON-DOPEDSILICON OXIDE DIELECTRIC MATERIAL OF AN INTEGRATED CIRCUIT STRUCTURE,AND REMOVAL OF RESIDUES FROM VIA ETCH AND RESIST MASK REMOVAL”, assignedto the assignee of this application, and the subject matter of which ishereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for an integrated circuit structurehaving a layer of low k carbon-doped silicon oxide dielectric material.More particularly, this invention relates to the removal of aphotoresist mask used to form an opening such as a via or a trench inthe low k dielectric material and the removal of residues from both theetching of the opening and the subsequent resist mask removal.

2. Description of the Related Art

In the continuing reduction of scale in integrated circuit structures,both the width of metal interconnects or lines and the horizontalspacing between such metal lines on any particular level of suchinterconnects have become smaller and smaller. As a result, horizontalcapacitance has increased between such conductive elements. Thisincrease in capacitance, together with the vertical capacitance whichexists between metal lines on different layers, results in loss of speedand increased cross-talk. As a result, reduction of such capacitance,particularly horizontal capacitance, has received much attention. Oneproposed approach to solving this problem of high capacitance is toreplace the conventional silicon oxide (SiO₂) dielectric material,having a dielectric constant (k) of about 4.0, with another dielectricmaterial having a lower dielectric constant to thereby lower thecapacitance.

In an article by L. Peters, entitled “Pursuing the Perfect Low-KDielectric”, published in Semiconductor International, Volume 21, No.10, September 1998, at pages 64-74, a number of such alternatedielectric materials are disclosed and discussed. Included in thesedielectric materials is a description of a low k dielectric materialhaving a dielectric constant of about 3.0 formed using a chemical. vapordeposition (CVD) process developed by Trikon Technologies of Newport,Gwent, U.K. The Trikon process is said to react methyl silane (CH₃—SiH₃)with hydrogen peroxide (H₂O₂) to form monosilicic acid which condenseson a cool, wafer and is converted into an amorphous methyl-doped siliconoxide which is annealed at 400° C. to remove moisture.

An article by S. McClatchie et al. entitled “Low Dielectric ConstantOxide Films Deposited Using CVD Techniques”, published in the 1998Proceedings of the Fourth International Dielectrics For ULSI MultilevelInterconnection Conference (Dumic) held on Feb. 16-17, 1998 at SantaClara, Calif., at pages 311-318, also describes the formation ofmethyl-doped silicon oxide by the low-k Flowfill process of reactingmethyl silane with H₂O₂ to achieve a dielectric constant of ˜2.9.

The use of low k carbon-doped silicon oxide dielectric material formedby reacting methyl silane with hydrogen peroxide (the Trikon process)has been found to be capable of better gap filling characteristics thanother low k materials. Good gap filling characteristics, in turn, canresult in the formation of void-free filling of the high aspect ratiospace between parallel closely spaced apart metal lines with dielectricmaterial having a lower dielectric constant than that of conventionsilicon oxide, thereby resulting in a substantial lowering of thehorizontal capacitance between such adjacent metal lines on the samemetal wiring level.

However, it has been found that the bond formed between the siliconatoms and the organic groups in a carbon-doped silicon oxide dielectricmaterial is not as stable as the silicon-oxygen bond found inconventional silicon oxide (SiO₂) materials. For example, unprotectedsurfaces of such a low k carbon-doped silicon oxide dielectric materialmay be exposed to oxidizing or “ashing” systems, which areconventionally used to remove a photoresist mask from the layer of low kcarbon-doped silicon oxide dielectric material, after formation ofopenings, such as vias, therein. It has been found that the ashingprocess results in damage to the bonds (cleavage) between the organicgroups and the silicon atoms adjacent the surfaces of the layer of low kcarbon-doped silicon oxide dielectric material exposed to such an ashingtreatment. This cleavage of the carbon-silicon bonds, in turn, resultsin removal of such organic materials formerly bonded to the siliconatoms, along with removal of the organic photoresist materials from theintegrated circuit structure. The silicon atoms from which the organicgroups have been cleaved, and which are left in the damaged surface oflow k carbon-doped silicon oxide dielectric material, are in a highlyreactive state and become water absorption sites if and when the damagedsurface is exposed to moisture.

This absorption of moisture by the damaged low k carbon-doped siliconoxide dielectric material, can result in hydroxyl bonding to thereactive silicon atoms left from the cleavage of the carbon-siliconbonds in the damaged surfaces of the low k carbon-doped silicon oxidedielectric material. This silicon-hydroxyl bond is not a stable bond,and subsequent exposure to heat, e.g., during subsequent processing suchas annealing, can result in cleavage of the silicon-hydroxyl bond,thereby causing water vapor formation which, for example, can interferewith subsequent filling of a via/contact opening or a damascene trenchwith metal filler material, resulting in what is known as via poisoning.

The upper surface of the low k carbon-doped silicon oxide dielectricmaterial can be protected from such attack during removal of the resistmask by provision of a protective layer, e.g. a capping layer ofconventional silicon oxide (dielectric constant k of ˜4) over the uppersurface. However, the use of the conventional ashing (oxidation) processto remove the resist mask causes physical damage to anycarbon-doped-silicon oxide material which is exposed in walls of vias,trenches, or contact openings, resulting in cracked, degraded, bowed,and porous insulating material in the walls of such openings. The poresin the walls of vias, trenches, or contact openings can present furtherproblems by retaining destructive gases produced during one or moresubsequent metal deposition steps. The physical damage to the insulatingmaterial which forms the walls of such openings cause the subsequentmetal deposition step to be unreliable; and the presence, in the porecavities, of gases produced during, metal deposition steps result in adegradation of the metal/metal nitride properties.

Sukharev et al. U.S. Pat. No. 6,114,259, assigned to the assignee ofthis invention, and the subject matter of which is hereby incorporatedby reference, teaches removal of the photoresist mask used to formopenings such as vias in low k carbon-doped silicon oxide dielectricmaterial in a two step process. wherein the etched via sidewalls of thelow k carbon-doped silicon oxide dielectric material are first treatedwith a nitrogen plasma, or a nitrogen and oxygen plasma, to densify theexposed low k carbon-doped silicon oxide dielectric material. Thephotoresist mask is then removed with a mild oxidizing agent comprisingan H₂O plasma. The H₂O plasma removes the resist mask without damagingthe exposed low k carbon-doped silicon oxide dielectric materialcomprising the sidewalls of the etched via sufficiently to interferewith later filling of the via with an electrically conductive metalfiller.

Wang et al. U.S. Pat. No. 6,028,015, also assigned to the assignee ofthis invention, and the subject matter of which is also herebyincorporated by reference, teaches treating damaged via sidewalls of lowk carbon-doped silicon oxide dielectric material with either a hydrogenplasma or a nitrogen plasma to repair the via sidewall surfaces whichhave been damaged by prior removal, of the photoresist mask with atraditional ashing/oxidation process, i.e., an oxygen plasma. Such atreatment with a hydrogen or nitrogen plasma is said to cause thehydrogen or nitrogen to bond to silicon atoms with dangling bonds leftin the damaged surface of the low dielectric constant carbon-dopedsilicon oxide insulation layer to replace organo material severed fromsuch silicon atoms at, the damaged surface. Absorption of moisture inthe damaged surface of the layer of low dielectric constant carbon-dopedsilicon oxide dielectric material, by bonding of such silicon withmoisture, is thereby inhibited.

Previously cited U.S. Pat. No. 6,316,354 discloses a process forremoving resist mask material from a protective barrier layer formedover a layer of low k carbon-doped silicon oxide dielectric material ofan integrated circuit structure without damaging the low k dielectricmaterial, and without the necessity of subjecting the exposed viasidewalls of the low k dielectric material to either a pretreatment toinhibit subsequent damage to the low k dielectric material during theresist removal, or a post treatment to repair damage to the low kmaterial after the resist removal. The resist removal process comprisesexposing the resist mask material to a hydrogen plasma formed from asource of hydrogen such as ammonia, while maintaining the temperaturebelow about 40° C. to inhibit attack of the low k silicon oxidedielectric material by oxygen released from the decomposition of theresist material.

Previously cited U.S. Pat. No. 6,562,700, describes a process forremoving a photoresist mask used to form openings in an underlying layerof low k carbon-doped silicon oxide dielectric material of an integratedcircuit structure formed on a semiconductor substrate, by exposing thephotoresist mask in a plasma reactor to a plasma formed using a reducinggas until the photoresist mask is removed. In a preferred embodiment thereducing gas is selected from the group consisting of NH₃, H₂, and amixture of NH₃ and H₂. The low k carbon-doped silicon oxide dielectricmaterial is then treated with a solvent capable of dissolving etchresidues left from forming the openings in the low k dielectricmaterial, and from removing the photoresist mask used to form theopenings in the low k carbon-doped silicon oxide dielectric material.The low k carbon-doped silicon oxide dielectric material is thenannealed in an annealing chamber at a temperature sufficient to removeliquid and gaseous-byproducts from the low k carbon-doped silicon oxidedielectric material.

While the substitution of a milder oxidation process using an H₂Oplasma, as proposed by Sukharev et al. U.S. Pat. No. 6,114,259, or thesubstitution of the reducing processes respectively proposed by Hu U.S.Pat. No. 6,316,354 and Gu et al. U.S. Pat. No. 6,562,700, constituteimprovements over the conventional oxidation or ashing process, it hasbeen found that the problem of via poisoning still is experienced at ahigher than desirable rate.

Thus, in the processing of low k carbon-doped silicon oxide dielectricmaterial in integrated circuit structures, it remains a goal to providefor the removal of residues from both the via etch step, and removal ofthe photoresist via mask, in a manner which will not interfere withsubsequent filing, with electrically conductive material such as metals,of the vias or other openings in the low k carbon-doped silicon oxidematerial.

SUMMARY OF THE INVENTION

The invention provides a process for removal of a photoresist mask usedto etch openings in a layer of low k carbon-doped silicon oxidedielectric material of an integrated circuit structure, and for removingetch residues remaining from either the etching of the openings or theremoval of the resist mask, while inhibiting damage to the low kcarbon-doped silicon oxide dielectric material, which comprises:exposing the integrated circuit structure to a plasma formed from one ormore reducing agents to remove at least a portion of the photoresistmask, and to remove at least a portion of the residues remaining fromformation of the openings in the layer of low k carbon-doped siliconoxide dielectric material. The integrated circuit structure is thenexposed to a plasma formed from one or more oxidizing agents to removeany remaining residues from both the formation of the openings in thelayer of low k carbon-doped silicon oxide dielectric material and theremoval of the resist mask.

In a preferred embodiment, the oxidizing etch is directional using onlycharged particles and not radicals to provide an anisotropic etching ofthe openings in the low k carbon-doped silicon oxide dielectric materialto thereby inhibit damage to the low k carbon-doped silicon oxidedielectric material comprising the sidewalls of the openings whileremoving the etch residues.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary vertical cross-sectional view of an openingetched in a low k carbon-doped silicon oxide dielectric material and ananisotropic beam of charged particles having an axis parallel to theaxis of the opening, passing into the opening during the oxidizing stepwith stray charged particles intersecting the side walls of the openingto remove the coating formed thereon during the prior reducing step.

FIG. 2 is a flowsheet illustrating the process of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the invention, a process is provided for removal of aphotoresist mask used to etch openings in a layer of low k carbon-dopedsilicon oxide dielectric material of an integrated circuit structure,and for removing etch residues remaining from either the etching of theopenings or the removal of the resist mask, while inhibiting damage tothe low k silicon oxide dielectric material. The process comprises firstexposing the integrated circuit structure to a plasma formed from one ormore reducing agents to remove at least a portion of the photoresistmask, and to remove at least a portion of the residues remaining fromformation of the openings in the layer of low k carbon-doped siliconoxide dielectric material or the residues remaining from removal of theresist mask or the residues remaining from both the formation of theopenings in the layer of low k carbon-doped silicon oxide dielectricmaterial and the removal of the resist mask.

Optionally, at this point, the integrated circuit structure may besubject to a wet solvent treatment to remove further etch residues. Aexample of such a solvent would be an EKC-265 hydroxy amine solventavailable from EKC Technology, Inc.

The integrated circuit structure is then exposed to a plasma formed fromone or more oxidizing agents to remove any remaining residues from boththe formation of the openings in the layer of low k carbon-doped siliconoxide dielectric material and the removal of the resist mask.

Optionally, after this oxidizing plasma step, the integrated circuitstructure may again be subject to a wet solvent treatment to removefurther etch residues, as described above. It should be emphasized,however, that the use of a wet solvent treatment, either after thereducing plasma step, or after the oxidizing step (or after both plasmasteps) is optional, and should only be used as needed.

In a preferred embodiment, the oxidizing etch is directional using onlycharged particles and not radicals to provide an anisotropic etching ofthe openings in the low k carbon-doped silicon oxide dielectric materialto thereby inhibit damage to the low k carbon-doped silicon oxidedielectric material comprising the sidewalls of the openings.

a. The Low K Carbon-Doped Silicon Oxide Dielectric Material

The term “low k dielectric material”, as used herein, is intended tomean a dielectric material having a dielectric constant k which is below4.0, preferably below 3.5, and most preferably below 3.0.

The low k carbon-doped silicon oxide dielectric material referred toherein comprises the reaction product of an organo-substituted silaneand an oxidizing agent. Examples of organo-substituted silanes includethe methyl silane referred to in the previously cited Peters andMcClatchie et al. articles. The organo-substituted silane may alsocomprise a multiple carbon-substituted silane such as described in U.S.Pat. No. 6,303,047, issued Oct. 16, 2001, and assigned to the assigneeof this invention, the subject matter of which is hereby incorporated byreference. The organo-substituted silane may also comprise anorganofluoro silane such as described in U.S. Pat. No. 6,365,528, issuedApr. 2, 2002, and in U.S. Pat. No. 6,572,925, issued Jun. 3, 2003 andSer. Nos. 09/792,685 and 09/792,691. All of the latter three of thepreceding cases were filed on Feb. 23, 2001. All four of theseapplications are assigned to the assignee of this application, and thesubject matter of all four applications is hereby incorporated byreference.

In a preferred embodiment the organo-substituted silane, such as any ofthose described above, is reacted with a mild oxidizing agent such ashydrogen peroxide to form a low k dielectric material capable of fillinghigh aspect ratio spaces between closely spaced apart structures such asraised lines without creating voids in such spaces.

b. The Reducing Step to Remove Resist Mask and Etch Residues

The reducing agent used in conjunction with the plasma to form areducing plasma may comprise a gas such. as, for example, ammonia (NH₃),hydrogen (H₂), or a mixture of either or both gases with nitrogen (N₂).As will be discussed below, it is deemed to be preferred that thereducing gas or mixture of gases contain both. hydrogen and nitrogenatoms which will respectively ionize to hydrogen and nitrogen ions. Theratio of nitrogen atoms to hydrogen atoms in the reducing gas or mixtureof gases will range from about 2:1 to about 1:2, and preferably fromabout 1.5:1 to about 1:1.5. The range of the flow of reducing gas orgases into the reactor will be equivalent to a flow of from about 50standard cubic centimeters per minute (sccm) to about 2000 sccm into a21 liter reactor.

The plasma power for the reducing plasma may range from about 200 wattsto about 1000 watts, with either the substrate and one side of the powersupply grounded or a second power supply connected to the substrate toprovide a bias on the substrate of from about 500 volts to about 1200volts. For the reducing plasma, it is preferred to have present bothcharged particles (ions) as well as uncharged reactive particles(radicals). Therefore, the reducing step should be carried out inequipment capable of generating charged particles (i.e., an RIE beam),but also radicals as well (i.e., a microwave generator). Commercialequipment capable of providing both a supply of uncharged radicals aswell as an anisotropic beam of ionized particles is available from ULVACTechnology, Inc. or Novellus Systems, Inc.

The reducing step of the process should be carried out in a reactor at apressure ranging from about 1 millitorr to about 1 torr whilemaintaining in the reactor a temperature of from about −20° C. to about70° C. The reducing step will usually be carried out for a period oftime sufficient to remove the desired, amount of residues, usuallyranging from about 10 seconds to about 5 minutes.

While we do not wish to be held to any theories of operation of theprocess, it is thought that the reducing plasma, while reacting with.the resist layer to remove some or all of the resist, may beinstrumental in forming an undesired coating of organic nitrogen on theexposed sidewall of the openings in the low k carbon-doped silicon oxidedielectric material, particularly when both nitrogen and hydrogen arepresent in the: reducing plasma. This sidewall coating is thought toform either by reaction of the reducing plasma with some of the etchresidues to form the coating, or by the reducing plasma reacting withthe low k carbon-doped silicon oxide dielectric material to form thecoating after removing the etch residues. In either case, the exposureof the low k sidewalls of the openings to the reducing plasma apparentlyresults in formation of an organo nitrogen coating on low k sidewallswhich may protect the low k dielectric from further attack by theplasma, unlike the conventional oxide ashing procedures used to removethe photoresist mask. However, this coating has ben found to be isunstable and may later interfere with the filling of the opening withelectrically conductive material unless it is removed. Formation of thiscoating is apparently enhanced when both hydrogen and nitrogen arepresent in the reducing plasma.

c. The Oxidizing Step to Remove Coatings and Etch Residues

On of the key functions of the subsequent oxidizing plasma, therefore,is to remove the coating formed on the sidewalls of the openings in thelow k carbon-doped silicon oxide dielectric material during the priorreducing plasma step without, however, damaging the low k carbon-dopedsilicon oxide dielectric material as it becomes exposed during theremoval of the coating formed thereon.

It may be possible to carry out the oxidizing step, including removal ofthe coating, without damaging the low k carbon-doped silicon oxidedielectric material by careful control of each of the processparameters, and empirically determining the exposure time of thestructure to the oxidizing plasma.

However, in a preferred embodiment, the coating is removed from the lowk carbon-doped silicon oxide dielectric material in a more controllableand consistent manner by exposing the coating, and the underlying low kcarbon-doped silicon oxide dielectric material, as it becomes exposed,to an oxidizing plasma which contains substantially no reactiveuncharged particles such as radicals, but rather comprises a directionalbeam of charged particles which is directed down the central axis of theopening, i.e., parallel to the sidewall surfaces of the opening. In thismanner, only a small number of such charged particles stray from theoxidizing beam, but this small number of charged particles has beenfound to be sufficient, both in flux density and reactivity, to removethe coating over the low k carbon-doped silicon oxide dielectricmaterial, but insufficient to damage the underlying low k carbon-dopedsilicon oxide dielectric material exposed by this removal of thecoating. This treatment of the exposed surfaces of the low kcarbon-doped silicon oxide dielectric material with the anisotropicoxidizing plasma may also serve to densify the low k material, therebymaking the low k material less porous and more resistant to moisture orother contaminants.

Mitigation of damage to the low k carbon-doped silicon oxide dielectricmaterial is further enhanced by the absence of radicals which, ifpresent, might attack the low k carbon-doped silicon oxide dielectricmaterial as it became exposed by bombardment of the coating by thecharged particles. It is further believed that the use of an oxidizingbeam of charged particles may serve further to densify the exposedsurfaces of the low k carbon-doped silicon oxide dielectric material,particularly during about the first ten seconds of the oxidizing step.

FIG. 1 illustrates the coating removal aspect of the invention, usingthe anisotropic charged particle only oxidizing plasma. An integratedcircuit structure is generally illustrated at 2 having formed thereon alayer 4 of low k carbon-doped silicon oxide dielectric material havingan opening 10 such as a via previously etched therethrough. Layer 6shown formed over low k layer 4 comprises a protective capping layer ofdielectric material (e.g., conventional silicon oxide) which protectsthe upper surface of the low layer. During removal of the photoresistmask and the etch residues by a previous treatment with a reducingplasma, a coating layer 14 forms on the sidewalls of opening 10 whichcoating layer is to be removed by the directional beam of chargedoxidizing particles having its main axis 20 parallel to the sidewalls ofopening 10 and coating 14 thereon. It will be noted that while the mainflux of particles continues to travel along axis 20 of the beam, straycharged particles stray from the path to intersect and bombard coating14, resulting in the eventual removal of coating 14 from the sidewallsof opening 10.

The oxidizing plasma, used to remove the residues and theabove-discussed coating remaining after exposure to the reducing plasma,may be formed using oxygen gas (O₂). or preferably a mixture of oxygenwith another gas, such as nitrogen or argon gas. In a particularlypreferred embodiment, a mixture of oxygen and argon is used to form theoxidizing plasma. The oxygen/argon ratios may vary from 100 volumepercent (vol. %) oxygen and 0 vol. % argon to 5 vol. % oxygen and 95vol. % argon. Typically, the ratio of oxygen to argon is about 50 vol. %of each gas. The range of the flow of oxidizing gas or gases (O₂+N₂ orO₂+Ar) into the reactor will be equivalent (for each gas) to a flow offrom about 10 standard cubic centimeters (sccm) to about 500 sccm into a21 liter reactor.

As discussed above, the oxidizing plasma step is preferably carried outusing equipment which excludes uncharged radicals, but rather suppliesonly a beam of charged particles. Commercial equipment capable ofproviding an anisotropic beam of ionized particles (RIE apparatus) isavailable from ULVAC Technology, Inc. or Novellus Systems, Inc.

The oxidizing step of the process should be carried out in a reactor ata pressure ranging from about 100 millitorr to about 10 torr whilemaintaining in the reactor a temperature of from about 10° C. to about70° C. The oxidizing step will usually be carried out for a period oftime sufficient to remove the coating formed on the sidewalls of theopenings during the reducing step, as well as any remaining residues,usually ranging from about 10 seconds to about 3 minutes.

d. EXAMPLE

To further illustrate the process of the invention, a number of testsubstrates were prepared, each having integrated circuit structurespreviously formed thereon including an intermetallic layer and aninsulating layer of low k carbon-doped silicon oxide dielectric materialhaving a number of vias etched therein through a photoresist mask formedover a protective capping layer of oxide on the layer of low kcarbon-doped silicon oxide dielectric material.

The substrates were first placed into a 21 liter reactor capable ofproviding a plasma-containing both uncharged radicals and chargedparticles. The substrates were subjected to a reducing. plasma to removethe photoresist mask and at least a portion of the etch residuesremaining from formation of the vias through the layer of low kcarbon-doped silicon oxide dielectric material. Into the reactor wasflowed 350 sccm of ammonia, while maintaining the pressure in thereactor at a pressure of about 0.2 torr. The temperature of thesubstrates in the reactor was maintained at about 30° C. A plasma wasignited in the reactor and held at a power level of about 500 watts fora period of about 3 minutes, after which the plasma was extinguished.

Using the same reactor used above, all of the substrates were thenoriented in the reactor so that the substrates were each orthogonal tothe particle beam to be generated in the reactor, so that the axis ofthe charged particle beam would be parallel to the axis of the openingsin the substrate. Into the reactor was flowed 100 sccm of O₂ and 100sccm of Ar, while maintaining the reactor at a pressure of about 0.2torr, and the temperature at about 30° C. While operating the reactor ina RIE mode, an oxidizing plasma was ignited in the reactor andmaintained at a power level of about 500 watts for about 30 seconds,after which the plasma was extinguished.

The substrates were then removed from the reactor and some of thesubstrates were subject to a wet cleaning solvent treatment by immersionof the substrates into an EKC-265 cleaning solution for a period ofabout 20 minutes to remove further remaining residues: These wet cleanedsubstrates were then rinsed in DI water and dried.

A thin layer of titanium capable of promoting adherence (a “glue layer”)was then deposited by PVD (sputtered) over the surfaces of the etchedand cleaned openings in the low k dielectric material on all of thesubstrates. A CVD barrier layer of titanium nitride was then formed overthe titanium layer. The coated or lined openings were then filled with aconductive metal filler material. All of the substrates, having openingsin the low k dielectric material thereon cleaned in accordance with theinvention, were found to have a reduced number of unfilled orunsatisfactorily filled openings in the layer of low k dielectricmaterial thereon.

Having thus described the invention what is claimed is:
 1. A process forremoving etch residues from vias and for removing a photoresist maskused to form said vias in low k carbon-doped silicon oxide dielectricmaterial while inhibiting damage to said low k silicon oxide dielectricmaterial which comprises: a) exposing said photoresist mask and saidvias to a plasma formed from one or more reducing agents to remove atleast a portion of said resist mask and at least a portion of said etchresidues in said vias; and b) then exposing said vias and any remainingportions of said resist mask to a plasma formed from one or moreoxidizing agents to remove the remainder of said etch residues in saidvias and any remaining portions of said photoresist mask said step ofexposing said vias and any remaining portions of said resist mask to aplasma formed from one or more oxidizing agents further comprisesexposing said remainder of said etch residues in said vias and anyremaining portions of said photoresist mask to a directional beam ofcharged particles from said plasma formed from one or more oxidizingagents, and said directional beam of charged particles is furthercharacterized by the substantial absence of radicals.
 2. The process ofclaim 1 wherein said one or more reducing agents are selected from thegroup consisting of ammonia, hydrogen, a mixture of ammonia andhydrogen, a mixture of ammonia and nitrogen, a mixture of hydrogen andnitrogen, and a mixture of ammonia, hydrogen, and nitrogen.
 3. Theprocess of claim 1 wherein said one or more reducing agents includes asource of hydrogen and a source of nitrogen.
 4. The process of claim 1wherein said plasma formed from said one or more reducing agentscontains radicals and charged particles.
 5. The process of claim 1wherein said one or more oxidizing agents used to form said plasmaincludes oxygen.
 6. The process of claim 1 wherein said one or moreoxidizing agents used to form said plasma comprises a combination ofoxygen and at least one further gas.
 7. The process of claim 1 whereinsaid one or more oxidizing agents used to form said plasma comprises acombination of oxygen and at least one further gas selected from thegroup consisting of nitrogen and argon.
 8. The process of claim 1wherein said one or more oxidizing agents used to form said plasmaconsists essentially of a combination of oxygen and argon.
 9. Theprocess of claim 1 wherein said step of exposing said photoresist maskand said vias to a plasma formed from one or more reducing agentsfurther includes forming a coating on the sidewalls of said vias. 10.The process of claim 9 wherein said step of exposing said vias and anyremaining portions of said resist mask to a plasma formed from one ormore oxidizing agents further includes removing said coating formed onsaid sidewalls of said vias.
 11. The process of claim 1 wherein saidstep of exposing said photoresist mask and said vias to a plasma formedfrom one or more reducing agents further includes forming said plasmafrom one or more reducing agents which includes hydrogen and nitrogensand an organo nitrogen coating forms on the sidewalls of said vias. 12.The process of claim 11 wherein said step of exposing said vias and anyremaining portions of said resist mask to a plasma formed from one ormore oxidizing agents further includes removing said organo nitrogencoating formed on said sidewalls of said vias.
 13. The process of claim1 which includes the further step of exposing said etch residues fromformation of said vias and removal of said photoresist mask to a wetsolvent to remove further residues.
 14. A process for removing etchresidues from vias and for removing a photoresist mask used to form saidvias in low k carbon-doped silicon oxide dielectric material whileinhibiting damage to said low k silicon oxide dielectric material usinga reducing plasma followed by an oxidizing plasma by which comprises: a)exposing said photoresist mask and said vias to a plasma formed from oneor more reducing agents selected from the group consisting of ammonia,hydrogen, a mixture of ammonia and hydrogen, a mixture of ammonia andnitrogen, a mixture of hydrogen and nitrogen, and a mixture of ammonia,hydrogen, and nitrogen, to remove at least a portion of said resist maskand at least at least a portion of said etch residues in said vias; andb) then exposing said vias and any remaining portions of said resistmask to a directional beam of charged particles from a plasma of saidone or more oxidizing agents, and further characterized by thesubstantial absence of uncharged radicals, said one or more oxidizingagents further comprising a combination of oxygen and at least onefurther gas selected from the group consisting of nitrogen and argon, toremove the remainder of said etch residues in said vias and anyremaining portions of said photoresist mask.